March 31 (Bloomberg) -- Prana Biotechnology Ltd. plunged
the most ever in New York after the company’s experimental drug
for Alzheimer’s disease failed to help patients in a trial.

The treatment, PBT2, didn’t show a statistically
significant reduction in the levels of beta-amyloid plaques in
the brains of people with mild Alzheimer’s, the Armadale,
Australia-based company said in a statement today. PBT2 also led
to no improvement in brain metabolic activity, cognition and
function, Prana said.

“Whilst not meeting all of our hopes, this result does not
deter us from the future development of PBT2, a safe and well-tolerated drug candidate for Alzheimer’s disease,” Chief
Executive Officer Geoffrey Kempler said in the statement.

The failure adds to the list of once-promising experimental
treatments for Alzheimer’s that have proven disappointing in
clinical trials. Since 1998, there have been more than 100
unsuccessful attempts to develop a drug for the malady, which is
the most common form of dementia. Worldwide about 35.6 million
people have dementia, the World Health Organization estimated in
2012.

Prana’s American depositary receipts dropped 72 percent to
$2.80 at 4 p.m. New York time, their biggest one-day drop since
the ADRs began trading in 2002. The ADRs had tripled this year
before today, valuing the company at $423.5 million.

PBT2 aims to prevent the accumulation of amyloid plaques,
growths in the brain that are hallmark of Alzheimer’s, by
interfering with metal ions that let them aggregate. The mid-stage study, dubbed Imagine, looked at 42 people with
Alzheimer’s. PBT2 was given to 27 of them, and the other 15
received a placebo.